Sliding window and door frame assemblies are well known. Such assemblies typically consist of an outer frame and a pair of inner or sash frames mounted within the outer frame, each holding a sealed glass unit. One or both of the sash frames are slidable relative to the outer frame to open or close the window or door.
Interlocks are known in the prior art for releasably securing two sash frames together when they are in a fully closed position. For example, U.S. Pat. No. 4,064,653, which issued to Randall et al on Dec. 27, 1977, relates to a sliding window having sash frames with mating tongues. The tongues engage each other and interlock when the window is closed so that the sashes will not be able to move transversely away from one another. Each tongue is formed on a vertical metal bar secured to an end rail of a sash frame. Randall et al also teaches weather sealing strips slidably mounted on each vertical bar which are received in a slot formed in a bar of the other sash frame when the window is closed. The sealing strips are connected to the sash rails that support them so that the adjoining rails and bars can slide vertically along the sealing strips when the windows are being installed or removed from the outer window frame.
One shortcoming of the Randall et al arrangement is that both sash frames require symmetrical, interengaging bars and sealing strips in order to achieve an effective interlock. Moreover, additional sealing strips or beads are required for engaging the window panes themselves, further increasing costs and complicating window frame assembly.
The need has arisen for a simplified, two piece interlock for a sliding window or door frame assembly comprising a glazing bead secured to one of the sash frames and a slidable seal secured to the glazing bead and extending vertically between the sash frames when the window or door is closed.